System and method for in-vivo imaging

ABSTRACT

An in-vivo imaging device including a camera may include a frame storage device. Systems and methods which vary the frame capture rate of the camera and/or frame display rate of the display unit of in-vivo camera systems are discussed. The capture rate is varied based on physical measurements related to the motion of the camera. Alternatively, the frame capture rate is varied based on comparative image processing of a plurality of frames. The frame display rate of the system is varied based on comparative image processing of a multiplicity of frames. Both the frame capture and the frame display rates of such systems can be varied concurrently.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. Ser. No.10/705,982, filed on Nov. 13, 2003 now U.S. Pat. No. 7,022,067 andentitled “SYSTEM AND METHOD FOR CONTROLLING IN VIVO CAMERA CAPTURE ANDDISPLAY RATE”, which in turn is a continuation application of U.S. Ser.No. 09/571,326, filed on May 15, 2000 now U.S. Pat. No. 6,709,387 andentitled “SYSTEM AND METHOD FOR CONTROLLING IN VIVO CAMERA CAPTURE ANDDISPLAY RATE”, each of which being incorporated in its entirety byreference herein.

FIELD OF THE INVENTION

The present invention relates generally to an in-vivo camera system and,in particular, to a system and method for controlling the frame capturerate and frame display rate of images produced by such a camera system.

BACKGROUND OF THE INVENTION

Several in-vivo measurement systems are known in the art. They includeswallowable electronic capsules which collect data and which transmitthe data to a receiver system. These intestinal capsules, which aremoved through the digestive system by the action of peristalsis, areused to measure pH (“Heidelberg” capsules), temperature (“CoreTemp”capsules) and pressure throughout the gastrointestinal (GI) tract. Theyhave also been used to measure gastric residence time, which is the timeit takes for food to pass through the stomach and intestines. Theseintestinal capsules typically include a measuring system and atransmission system, where a transmitter transmits the measured data atradio frequencies to a receiver system.

Endoscopes are other types of devices that obtain images from thegastrointestinal tract. There are currently two types of endoscopes.Fiber-optic endoscopes are pushed through the GI tract and use a fiberoptic waveguide to transmit a light signal from the area of interest toelectronics located outside the patient's body. Video endoscopes placean electronic camera at the area of interest and transfer the video datathrough a flexible cable to electronics located externally.

U.S. Pat. No. 5,604,531, assigned to the common assignee of the presentapplication and incorporated herein by reference, teaches an in-vivomeasurement system, in particular an in-vivo camera system, which iscarried by a swallowable capsule. In addition to the camera system thereis an optical system for imaging an area of the GI tract onto the imagerand a transmitter for transmitting the video output of the camerasystem. The overall system, including a capsule that can pass throughthe entire digestive tract, operates as an autonomous video endoscope.It images even the difficult to reach areas of the small intestine.

Reference is now made to FIG. 1 which shows a block diagram of thein-vivo video camera system described in U.S. Pat. No. 5,604,531. Thesystem captures and transmits images of the GI tract while passingthrough the gastro-intestinal lumen. The system contains a storage unit19, a data processor 14, a camera 10, an image transmitter 8, an imagereceiver 12 (often an antenna array), which usually includes an antennaarray, and an image monitor 18. Storage unit 19, data processor 14,image monitor 18, and image receiver 12 are located outside thepatient's body. Camera 10, as it transits the GI tract, is incommunication with image transmitter 8 located in capsule 6 and imagereceiver 12 located outside the body. Data processor 14 transfers framedata to and from storage unit 19 while the former analyzes the data.Processor 14 also transmits the analyzed data to image monitor 18 wherea physician views it. The data can be viewed in real time or at somelater date.

The number of pictures that need to be taken and which must be analyzedby the attending physician is great. Assuming a minimum of two imagesper second and a four to five hour dwell time in the GI tract, 30,000images would be required during the transit of the GI tract by thecapsule. If 20 frames per second (fps) are displayed as is standard, thephysician would need about 30 minutes to examine the images of theentire GI lumen.

PCT Application PCT/IL98/00608, published as WO 99/30610 and IsraeliApplication 122602 assigned to the common assignee of the presentapplication and incorporated herein by reference, recite a method forreducing the number of frames captured by an in-vivo camera, therebyextending its life. The method discussed in the aforesaid applicationsrequires disconnecting the camera 10 from the power source when motion(velocity) is below a certain threshold value.

SUMMARY OF THE PRESENT INVENTION

It is an object of the present invention to provide a system and methodfor minimizing the time for reviewing images taken by an in-vivo camerasystem or by endoscopes. This is accomplished by either varying the rateof data display and/or varying the rate of data acquisition.

In one embodiment of the present invention, an in-vivo camera systemincludes an imager which can have its frame capture rate varied. It alsoincludes at least one sensor for measuring a physical property relatableto the motion of the camera system, a data processor for determining aframe capture rate after receiving data from the sensor, and acontroller for supplying the determined frame capture rate to theimager. The sensor can be, among other things, an accelerometer, anaccelerometer connected to an integrator, a pressure sensor, aninduction coil, or an ultrasonic transducer.

In another embodiment, an in-vivo camera system includes an imager whichcan have its frame capture rate varied, a storage device for storingframes captured by the imager, an image processor for calculating therequired frame capture rate from at least two frames, and a controllerfor supplying the calculated frame capture rate to the imager.

In yet another embodiment of the present invention, a display system fordisplaying the output of an in-vivo camera system is described. Thesystem includes a frame storage unit for storing frames of the camerasystem, and an image processor for correlating frames to determine theextent of their similarity. The processor generates a frame display ratewhich is slower when the frames are generally different and faster whenthe frames are generally similar. The embodiment also includes a displayunit for displaying the frames received from the frame storage unit atthe frame display rate. The display system described can also include acontroller connected to a frame storage unit and the imager processor.The controller then varies the display rate of the aforementioneddisplay unit. In the above embodiment the at least two frames can beconsecutive or non-consecutive frames.

In still another embodiment a video camera system also includes adisplay system having a frame storage unit for storing at least twoframes and an image processor for determining the similarity of at leasttwo frames. The processor generates a frame display rate based on thesimilarity of the frame. The frame display rate is slower when theframes are generally different and faster when the frames are generallysimilar. The embodiment also includes a display unit for displaying theframes received from the frame storage at the required frame displayrate.

In yet another embodiment an in-vivo camera system also includes adisplay system having a frame storage unit for storing at least twoframes. The display system further includes an image processor forcorrelating at least two frames thereby determining the extent of theirsimilarity and for generating a frame display rate based on thatsimilarity. Finally, the display system includes a display unit fordisplaying the frames received from the frame storage at the framedisplay rate.

In one embodiment of the present invention, a method is taught forvarying the frame capture rate of a series of frames generated by anin-vivo camera system. The method includes the steps of storing theframes in a storage device, correlating changes in the details of atleast two frames, changing the frame capture rate to a predeterminedframe capture rate according to the degree of change between the atleast two frames and transmitting the capture rate to the imager.

In another embodiment, a method is taught for varying the frame capturerate of a series of frames generated by an in-vivo camera system. Themethod includes the steps of measuring a physical quantity experiencedby the camera system, converting the physical quantity to a velocity ofthe camera, correlating the velocity with a predetermined frame capturerate, and transmitting the predetermined capture rate to the imager. Thestep of measuring includes the step of measuring acceleration, pressure,induced current or motion, the latter with an ultrasonic transducer.

In yet another embodiment of the present invention, a method is taughtfor varying the frame display rate of a series of frames generated by anin-vivo camera system, the method including the steps of storing theframes in a storage device, correlating changes in the details of atleast two frames, and transmitting the required frame display rate to astorage device and a display unit.

Yet a further embodiment of the present invention teaches a method forvarying the frame display rate of a series of frames generated by anin-vivo camera system which includes the step of repeating the displayof a frame a predetermined number of times.

A similar further embodiment teaches a method for varying the framedisplay rate of a series of frames generated by an in-vivo camera systemwhich includes the step of eliminating the display of at least oneframe.

The system may include an imager for producing frames and a storagedevice for storing frames.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully fromthe following detailed description taken in conjunction with thedrawings in which:

FIG. 1 is a block diagram illustration of a prior art in-vivo videocamera system;

FIG. 2 is a block diagram illustration of a system for varying the framecapture rate of the camera system of FIG. 1 using a sensor to determinechanges in video capsule velocity;

FIG. 3A is a block diagram illustration of a further embodiment of FIG.2 using an accelerometer as a sensor;

FIG. 3B is a block diagram illustration of a still further embodiment ofFIG. 2 using an accelerometer as a sensor with the control loop andsensor all inside the capsule;

FIG. 4 is a block diagram illustration of an alternative embodiment ofthe system of FIG. 1 in which image data from two consecutive frames iscompared;

FIG. 5 is a block diagram illustration for varying the frame displayrate of the in-vivo video camera system of FIG. 1 by comparing imagedata from two consecutive frames;

FIG. 6 is a block diagram illustration of a method for determining ifthe capsule has moved and a change in frame display rate is required;

FIG. 7 are histogram illustrations of a difference function useful inunderstanding the method of FIG. 6;

FIG. 8A is a block diagram illustration of a method for varying both theframe display rate and the frame capture rate as described in FIGS. 4and 5; and

FIG. 8B is a block diagram illustration of a system as in FIG. 8A butalso including a command processor.

Similar elements in different figures are given identical numbersthroughout.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The large volume of data collected by an in-vivo camera system, such asthe one described above, is a result of the long period of time, usuallyseveral hours, that it takes the camera to traverse thegastro-intestinal tract. The camera transits the GI tract in fits andstarts. Because of the intermittent motion of the capsule and its longresidence time at some positions, the number of sequential images thatare similar is very large. It would be preferable if such duplicativeframes were eliminated entirely or at least reduced in number.Alternatively, the display time of individual frames can be shortened,thereby reducing the time required to view the image data stream. Thepresent invention describes a number of ways to shorten viewing time:reducing the frame capture rate (FIGS. 2-4) and/or reducing the framedisplay rate (FIG. 5).

It should be understood that in all discussions both above and below,when the terms camera and imager are used they are equivalent. It shouldalso be understood that the camera or imager being discussed in thisapplication is one capable of having its frame capture rate and/or framedisplay rate varied.

One method to control the frame capture rate is to monitor the velocityof the capsule in the GI tract. Reference is now made to FIG. 2, whichillustrates, in block diagram format, a system for controlling the framecapture rate of the camera 10. The system comprises a sensor 11, a dataprocessor 14, a frame capture rate controller 17, a frame capture ratetransmitter 16, a capture rate receiver 9, camera 10 and optionally, adatabase or look-up table 15. Camera 10 and capture rate receiver 9 areboth located within the capsule.

Sensor 11, which measures motion directly or indirectly, is attached to,or placed within, the capsule 6 and relays the value of a measuredmotion-related physical property to data processor 14. Data processor14, together with database (or a look-up table) 15 to which processor 14is linked, determines the required frame capture rate based on currentand past values of the measured property. When the camera is movingslowly, fewer frames need to be captured; when it moves quickly, thenumber of frames captured or displayed needs to be increased. Dataprocessor 14 then provides the calculated capture rate to frame capturerate controller 17, which, in turn, transmits the rate to camera 10. Forclarity, FIG. 2 (as well as all later Figures) does not show the imagetransmitter 8 and image receiver 12 described above which is the actuallink between sensor 11 and data processor 14.

In the above embodiment, a database or look-up table is used. In otherembodiments, database or look-up table 15 is not needed and processor 14calculates the required frame capture rate directly using a suitablefunction.

FIG. 2 illustrates how the capture rate is transmitted to camera 10.Frame capture controller 17 transfers the desired frame capture rate toframe capture rate transmitter 16. Both controller 17 and transmitter 16are outside the patient's body. Transmitter 16 transmits informationabout the required capture rate to capture rate receiver 9 locatedwithin capsule 6. Capture rate receiver 9 then adjusts the frame capturerate of camera 10.

A special case of the system in FIG. 2 is illustrated in FIG. 3A wherethe sensor is an accelerometer 111 whose output is processed by anintegrator 13. The processor is a motion processor 114. The remainingelements are as shown in FIG. 2. Accelerometer 111 is in communicationwith integrator 13. Accelerometer 111, which is typically placed in theinterior of capsule 6, determines the instantaneous acceleration ofcapsule 6 as it moves through the GI tract. Integrator 13 converts theacceleration data to velocity. Integrator 13 can be a stand-aloneelement connected to motion processor 114 (as in FIG. 3A) or it can bean integral part of motion processor 114. In either case, integrator 13transfers information regarding the velocity of the capsule to motionprocessor 114. Motion processor 114, together with database (or look-uptable) 15, determines the required frame capture rate. Processor 114relays the calculated capture rate to frame capture rate controller 17.As described above (FIG. 2), frame capture controller 17 relays therequired frame capture rate via frame capture rate transmitter 16 tocapture rate receiver 9 within capsule 6.

In lieu of database (or look-up table) 15 in FIG. 3A, motion processor114 can utilize a function that relates velocity to frame capture rate.The function can then be used to calculate the required rate. Thefunction, capture rate vs. capsule velocity, will usually bemonotonically increasing.

The small accelerometer 111 used in FIG. 3A can be purchased fromnumerous suppliers. A suitable integrator 13 can also be obtained frommany different vendors. Alternatively, an integrator can be built usingan operational amplifier or implemented numerically using an A/Dconverter and a microprocessor.

In another embodiment, the integrator can be omitted from FIG. 3A. Inthat case, data from the accelerometer 111 can be processed directly todetermine the required frame capture rate.

The system in FIG. 1 has been shown and described with processing andstorage units outside the body, but they do not have to be. Throughminiaturization of the components, most, if not all, electronic elementsin FIGS. 2 and 3A above and FIGS. 4, 5 and 8 below, can be attached toor placed within capsule 6 and in direct communication with camera 10.

In fact, for the embodiments illustrated in FIGS. 2 and 3A, a similarbut alternate placement of components is possible. Referring to FIG. 3B,the previous embodiments would have sensor 11 (or accelerometer 111),integrator 13, data processor 14, and frame rate controller 17positioned inside capsule 6 and in direct communication with camera 10.Frame rate transmitter 16 and capture rate receiver 9 would then besuperfluous.

Other sensors can be used which can determine velocity. A pressuresensor attached to the capsule is one such sensor. When the rate ofperistalsis increases, velocity of the capsule through the smallintestine increases. A pressure sensor can detect peristaltic inducedpressure (and/or changes in pressure) exerted by the walls of the smallintestine. The relation between pressure (and/or changes in pressure)and velocity can be determined empirically, and then utilized todetermine the frame capture rate.

If the patient is placed in a magnetic field, capsule 6 can contain aninduction coil which functions as a velocity sensor. The magnetic fieldinduces a current in the coil whose magnitude is a function of thevelocity of the coil through the field. Data on the induced current istransmitted to motion processor 114 and processed as in FIG. 3A.

While the sensors 11 discussed with FIGS. 2 and 3 above are in-vivosensors and are attached directly to capsule 6, external sensors canalso be used. A Doppler ultrasound unit continuously tracking thecapsule can serve as an external sensor. Such a unit would be incommunication with motion processor 114 which would process velocitydata and convert it to a frame capture rate as discussed hereinabove.The conversion of ultrasonic Doppler data to velocity data is well-knownin the art. Once the velocities have been calculated, a function,database or look-up table can be used to define the desired capturerate.

In yet another embodiment, several physical properties are measuredconcurrently and used to determine an optimum frame capture rate. Thisembodiment requires multiple sensors 11, each attached to the capsule 6,or possibly, as with an ultrasound sensor, outside the body. Each sensorwould measure a different property. A data processor 14 or 114 as inFIGS. 2 and 3, or even a set of processors 14, one for each propertybeing measured, interprets the data and determines a suitable framecapture rate. The analyses performed by the several processors arerelayed to a central command processor (not shown) where their resultsare combined to obtain an optimum overall frame capture rate. Theoverall optimal rate is then relayed from the central command processorto frame capture rate controller 17, which transmits it to camera 10 ina manner identical to that described in FIG. 2.

In all of the above embodiments where the velocity of the capsule isdetermined, the conversion of velocity data to frame capture rate doesnot necessarily require the use of digital data. Analog data provided bythe sensor may be used directly to determine the required frame capturerate if proper ancillary analog circuitry is employed.

Reference is now made to FIG. 4 which illustrates another method forvarying the frame capture rate. FIG. 4 shows camera 10, storage unit 19,an image processor 214, frame capture controller 17 and optionally,database or look-up table 15. Camera 10 captures a frame that istransmitted as described in FIG. 1 to external storage unit 19. Imagesare stored sequentially in unit 19. The stored data is comprised of oneor more pixel properties. Color and intensity are among the propertiesthat can be stored.

Image processor 214 receives images for comparison from storage unit 19.Processor 214 compares each image I_(n) in the data stream to itspredecessor I_(n−1). If the stream of images is too lengthy or rapid,non-adjacent images can be compared, e.g. image I_(n) with the imageI_(n−k), where k>1. For this latter embodiment, the capture rate can becalculated for each k^(th) image, where k>0. As described below withrespect to FIG. 6, the comparison can be made on a pixel-by-pixel basisor, alternatively, on a pixel cluster basis. Based on the comparison ofthe two images, processor 214 calculates the required frame capturerate.

Frame capture rate controller 17 receives information about the requiredframe capture rate from image processor 214. As shown in FIG. 2 anddescribed above, controller 17 transfers the required frame capture rateto camera 10. For clarity, the requisite elements for this transfer havenot been included in FIG. 4 but can be seen in FIG. 2.

All of the methods discussed above relate to the frame capture rate. Analternative approach for reducing overall presentation time of thedatastream of the system is to use a variable frame display rate. Insuch situations, the frame capture rate can, but need not, be heldconstant. When the analysis of the pixels in consecutive framesindicates that the capsule is at rest or moving slowly, the images aredisplayed at a fast display rate. If the analysis indicates that thecapsule is moving rapidly through the GI tract, the images are displayedmore slowly.

Reference is now made to FIG. 5, where a block diagram illustrates sucha system. The diagram shows camera 10, storage unit 119, an imageprocessor 314, frame display rate controller 21, image monitor 18 and,optionally, database or look-up table 15. Camera 10 transmits frames tostorage unit 119. After the acquisition of a given number of frames andtheir storage in the buffer of storage unit 119, two consecutive framesP_(n) and P_(n−1), are sent to image processor 314. The frames, eitheron a pixel-by-pixel or pixel cluster basis, are compared using asuitable function or set of functions. The function will usually bemonotonically increasing. Image processor 314, based on its analysis ofthe compared frames, relays the required frame display rate to framedisplay controller 21. Frame display controller 21 provides the requiredframe display rate to storage unit 119. The latter releases an imageP_(m) or images P_(m) through P_(m+p) to image monitor 18. P_(m) may,but need not be, frames P_(n) or P_(n−1). As discussed above, it shouldbe remembered that the frame comparison need not be performed betweenadjacent images P_(n) and P_(n−1) but between P_(n) and P_(n−k), wherek>1.

The functions used by image processors 214 and 314 in FIGS. 4 and 5 tomake their determinations can be based on:

Calculating the simple difference in a given property betweencorresponding pixels of two, not necessarily consecutive, frames;

Calculating the cross-correlation function between two, not necessarilyconsecutive, frames; and

Calculating the changes of local statistical distributions β and betweencorresponding local statistical distributions β in two, not necessarilyconsecutive, frames.

Local statistical distributions can include the mean, the variance orthe standard deviation of given pixel clusters. The pixel cluster, forexample, can be the pixels in the upper left quadrant (64×64 pixels) ofa 256×256 image. The above approaches are illustrative only; otherapproaches may also be used.

When the image display rate is calculated for non consecutive images,P_(j) and P_(j+k), where k>1, the images P_(j+1) and P_(j+k−1), betweenthe non-consecutive images are speeded up or slowed done as determinedby the display rate calculation for frames P_(j) and P_(j+x).

Reference is now made to FIG. 6 where a block diagram of a functionwhich can be used to determine the required display rate is illustrated.FIG. 6 shows the operations needed for comparing image P_(i) andP_(i+x), where x is usually, but not necessarily, 1. Initially, eachimage P_(i) is divided (step 50) into a multiplicity of cellsA_(i)(m,n), where 1<m<M and 1<n<N.

The average intensity, I_(Ai(m,n)) of each cell A_(i)(m,n) of imageP_(i) is then calculated (step 52) from data provided by image receiver12 of FIG. 1. The absolute value of the difference D_(i)(k,l) of theaverage intensities I of A_(i)(k,l) and A_(i+x)(k,l) of correspondingcells A(k,l) in frames P_(i) and P_(i+x) is determined (step 54).D_(i)(k,l) is defined as:D _(i)(k,l)=|I _(A) _(i) _((k,l)) −I _(A) _(i+x) _((k,l))|It is readily apparent that where D_(i)(k,l) is small, the capsule ismoving slowly.

The D_(i)(k,l) values are then organized into a histogram (step 56). They-axis of the histogram is D_(i)(k,l) and the x-axis is the number ofcorresponding pairs of cells, A_(i)(k,l) and A_(i+x)(k,l), which have adifference of magnitude D_(i)(k,l). Referring to FIG. 7, curve (a)represents a histogram of essentially similar cells in consecutive (ornon-consecutive) frames, while curve (b) shows a histogram of cells insignificantly different frames. It should readily be apparent that iftwo images are similar, the histogram of the differences in the cells ofthese images are concentrated at low values of D_(i)(k,l). If the imagesare different, the histogram contains higher values of D_(i)(k,l). Itshould also be readily apparent that the center of mass CM_(a) of curve(a) is further to the right than the CM_(b) of curve (b) and representsa slower moving capsule.

Returning to FIG. 6, the center of mass CM of the histogram isdetermined in step 58. The CM of the histogram can be correlated (step60) with the velocity of the capsule by using an empirically determinedcorrelation supplied (step 66) by a database or look-up table. On thebasis of the CM of the histogram, a difference between images isdetermined and a velocity calculated (step 62). The capture or displayrate as a function of the difference or similarity in the comparedimages can be provided (step 68) from another empirically developeddatabase, look-up table or mathematical function. The capture or displayrate is then varied (step 64) accordingly.

Reference is now made to FIGS. 8A and 8B, which illustrate yet anotherembodiment of the invention. FIG. 8A shows a combined system where boththe frame capture rate and the frame display rate are variedconcurrently to minimize total data stream display time. FIG. 8A is afusion of the systems shown in FIGS. 4 and 5. There could equally wellhave been a combined system of the embodiments described in FIG. 2 or 3and 5.

In FIG. 8A, two storage units 19 and 119 and two image processors 214and 314 are shown. The system also includes frame capture ratecontroller 17, frame display rate controller 21, image monitor 18 andcamera 10. One storage unit 19 stores data for the frame capture rateanalysis while the other unit 119 stores data for the frame display ratecalculation. Each image processor 214 and 314 processes a different ratecalculation. Image processors 214 and 314 could use the same ordifferent algorithms to calculate the required capture and displayrates.

FIG. 8B is similar to FIG. 8A but contains a command processor 414 whichcoordinates and optimizes the capture and display rate calculations,while minimizing total presentation time. The command processor 414receives results calculated by processors 214 and 314 and transfers theoptimized overall rates to capture and display controllers 17 and 21respectively.

Currently, data is collected by the video camera at a rate of 2 framesper second (fps) and screened at a normal video rate of 30 fps. Thisscreening rate is too fast for the eye to discern changes and thedisplay rate must be slowed. An alternative to slowing down the displayrate is to repeat the same frame several times, displaying the repeatedframes at the standard rate. Repeating a frame is a way of changing thedisplay rate in cases where it is impossible to change the display rateof individual frames directly. Methods such as those discussed above,which measure the difference between corresponding pixels in two frames,can be used to determine if repetitive screening of the same frame isrequired. Repetition of frames, however, increases the total length ofthe data stream. Therefore, the processor must determine when thetrade-off between repeating frames and a longer, more time-consuming,data stream is advantageous.

It should be readily apparent, that if the capsule is moving too slowly,an inordinate number of frames may be identical. If that is the case,the frame rate controller, based on the pixel comparisons of the imageprocessor, can speed up the display rate by eliminating one or moreidentical frames.

It should also be readily apparent that the above-described methods forvarying frame capture and display rates can be applied to videoendoscopes with little or no modification.

It will be appreciated by persons skilled in the art that the presentinvention is not limited by what has been particularly shown anddescribed herein above. Rather the scope of the invention is defined bythe claims that follow:

1. An in vivo camera system comprising: a swallowable capsule forobtaining images from within a patient's gastrointestinal tract, thecapsule comprising an imager adapted to have its frame capture ratevaried; a processor to measure the movement of the capsule by comparingat least two images obtained thereby; and a transmitter external to thepatient, the transmitter to transmit to the capsule a frame capturerate, the imager to capture frames at the frame capture rate, which islower when the capsule movement is relatively slow and faster when thecapsule movement is relatively fast.
 2. The system according to claim 1,wherein the processor is to provide the capture rate to saidtransmitter.
 3. An in vivo camera system comprising: a swallowablecapsule for obtaining images from within a patient's gastrointestinaltract, the capsule comprising an imager adapted to have its framecapture rate varied; a processor to determine a frame capture rate forthe capsule by comparing at least two images obtained thereby; and atransmitter in communication with said processor, the transmitterexternal to the patient, the transmitter to transmit to the capsule theframe capture rate, the imager to capture frames at the frame capturerate, wherein the frame capture rate is lower when the capsule movementis relatively slow and faster when the capsule movement is relativelyfast.
 4. The system according to claim 3 wherein the processor is toprovide the capture rate to said transmitter.